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This blog is primarily for me to blog my responses to books that I'm reading. Sometimes I blog about other stuff too, though.

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Friday, August 21, 2015

Lies, damn lies, and PhD job statistics

Today I went to the physics student club room (a place where physics majors hang out and study and socialize) to drop off a few science magazines for them to read when they come back for fall quarter.  On a table I found this poster from the American Physical Society:

(A bit of Googling did not turn up a digital version of the poster.  If I find one I will link it.)

This looks like a pretty nice set of numbers for PhD employment.  64% in the private sector, 22% in potentially permanent academic jobs (which can be a sweet gig), and those in the private sector start at $92k.  Sweet!  What on earth could I be complaining about?

READ THE FINE PRINT!

Those numbers exclude postdoc positions and temporary academic jobs like adjuncting. What percentage of physics PhDs start off as postdocs or adjuncts?  According to the American Institute of Physics, 65%. 56% go into postdoc positions, and another 9% go into other short-term positions.  Now, most of them will eventually jump off of the postdoc/adjunct/visiting/etc. treadmill and find a full-time, long-term job that is reasonably satisfying.  That's great.  If APS wants to put those statistics out there, go for it.  However, they instead chose to lie with statistics, and put a really rosy picture of PhD job outcomes in big print, while putting a partial caveat in fine print, and never mentioning at all that their data only applies to 1/3 of new PhD graduates.

Now, if APS were a commercial organization attempting to sell something, well, caveat emptor.  The world is full of people telling incomplete stories.  The fact that it's ubiquitous does not make it right, but it does make it rather unremarkable.  There aren't enough hours in the day to blog about every misleading sales pitch ever made.  APS, however, is not a commercial organization.  APS is a non-profit professional society that exists to serve the physics community at all levels, including students.  (Indeed, off-camera the poster includes a link to this student membership site.)  Professional societies best serve their members when they provide their members with accurate data on careers and education.  APS is not serving the interests of their student members when they provide misleading statistical information to people who are trying to decide what to do after college.

Now, to be fair, they did include some information about careers for people with bachelor's degrees in the second half of the poster:




(For some reason Blogger is making it possible to zoom in on the first image but not these two.  I'm working on it.  And yes, I'm aware of the irony of making the fine print visible in only one image while complaining about people who are sweeping things under the rug.  I'll try to find a fix.)

The bottom figure certainly sells graduate school as The Path, by lumping graduate school, k-12 teaching, government jobs, and non-profit jobs in the same category.  It is clearly a slanted poster.  There's no good reason for this.  It is left as an exercise for the reader to figure out why an organization that ostensibly exists to serve all of its members would target college students with misleading statistics that might influence their post-graduation decisions.


Thursday, August 20, 2015

Mach-ing more sense

I've finished Mach's Science of Mechanics.  There's a lot that I don't feel like summarizing, but I will say a few things about the Bucket Problem.  After reading Mach's appendices, where he elaborates on the issue, it's pretty clear that Mach's stance on the bucket problem boils down to extreme skepticism.  All motion is measured relative to reference objects; otherwise experimental measurements would be impossible.  When we set a bucket in motion relative to the "fixed stars" in the sky, we see centrifugal forces, but we only know that it is in motion because we step back from it and observe points on the edge of the bucket being displaced relative to other objects that we treat as fixed.  It's not so much that Mach thought that there's an interaction between the bucket and the distant stars (maybe he did think that, maybe he didn't), it's that the measurements were relative to these objects and their frame, and we don't know enough about that frame to assert that there isn't something special about it.

(As an aside, it is strange that Mach attributed any significance to the "fixed stars" when Halley had demonstrated stellar motion in the early 1800's.)

Interestingly, Mach has a number of other prescient points.  He rejects the idea of motion relative to ether because nobody had identified a way to pick out and track particles of ether and watch motion relative to them.  Also, he made an interesting point about the optical-mechanical analogy in Hamiltonian mechanics.  The progress of mechanics as a science was to move away from supernatural notions, away from the Aristotelian idea that objects go to their preferred place in the cosmos, and away from the idea of the physical world acting out some divine plan.  However, the Principle of Least Action was a statement about nature optimizing something, and he refers to unnamed authors who see it as evidence of a plan.  Mach notes that Fermat's Principle of Least Time, describing the propagation of light rays, was at one time seen as evidence of an intelligent hand guiding light, until the synthesis of wave and ray theories showed that ray behavior emerges from wave behavior, and the Principle of Least Time emerges with it.  Mach's writing hints that the Principle of Least Action might yet be shown to be emergent from some larger theory.  Schrodinger, of course, supplied that theory.

Given that the Principle of Least Action shows us the traces of a larger theory, I have to reject Mach's assertion that Lagrangian mechanics is "merely" a more economical way to formulate the same set of physical ideas as Newton.  It is, rather, the cleanest trace of something bigger.

At the same time, though, I understand Mach's point that we should never confuse our theories and our taxonomy of physical concepts with the universe itself.  We like to do physics in certain bases, certain sets of variables.  However, the universe knows no fundamental basis.  Mach would surely agree with that, even if he was sympathetic to the possibility of the "fixed stars" providing a special reference frame.